Guide

Main Module | Energy from Mud? Thank a Microbe!
13
Background
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sediment and surface water environment where oxygen is limited. Two common
types of electrogenic bacteria, Shewanella (a.k.a “Mr. Clean”), and
Geobacter (a.k.a. “The Iron-Breather”).
Howmicrobialfuelcellsharnessenergyfrommicrobialmetabolism
(Please refer to the MudWatt diagram on page 16.)
Microbial fuel cells work because anaerobic bacteria create a thin lm on an
electrode buried in soils or sediment. These electrogenic bacteria deposit their
electrons onto the anode material (graphite ber).
Electrons ow through the wire from the anode to the cathode where electrons
combine with oxygen and hydrogen near the cathode to form water. The ow of
electrons from the anode to the cathode and back into the soil completes a circuit
and generates an electrical current.
A small circuit board with a capacitor and LED are visible indicators that electricity is
being produced.
For more information on electricity and circuits, see Sub-Module 2: Electricity and Circuits.
MudWatt Explorer App
The MudWatt Explorer App (available for most smartphones and tablets)
can be used to convert the number of blinks into current produced (in
microWatts (μW)). Additionally, students are able to use the MudWatt
PowerandMicrobePopulationCalculatorworksheetto estimate the
number of electron-donating microbes around their MudWatt’s anode.
• Measure your MudWatt’s power!
• Unlock chapters of a fun comic!
• Record and share your power data!
Download the MudWatt Explorer App!